1. Field of the Invention
The invention relates to a single-screw extruder for producing thermoplastic and elastomeric products, comprising a hollow cylindrical barrel, which is provided with inwardly protruding mixing elements, and a screw, which is disposed in the barrel and has one or more helical lands formed with recesses, through which the mixing elements are adapted to move as the screw is rotating.
2. Description of the Prior Art
From German Patent Publication Nos. 12 45 584 and 22 35 784, Published German Application Nos. 26 34 024 and 30 03 615, and the periodical "Kunststoffberater", 3/1984, page 25, for instance, it is known to provide pins, which extend through the barrel wall into the helical channel of the screw and move through the helical land or lands of the screw in recesses formed in said land or lands. Said pins ensure thorough mixing because they prevent rotation of the molten plastic material in unison with the screw.
In the known single-screw extruders, the mixing pins extend radially and are screwed into the integral barrel. That arrangement involves difficulties in assembly and has the disadvantage that wear, which usually occurs only at a few points, will render the entire housing unusable so that it must be replaced.